The present invention relates to an apparatus for automatically setting a welding condition used for arc welding.
Recently, the performance of arc welding power sources used for arc weldings such as CO.sub.2 weldings, MAG weldings or the like have made rapid progress, so that welding conditions can be easily set in comparison to the prior art, thereby improving welding quality as well. However, since a welding phenomenon is a non-linear phenomenon of a multi-input and multi-output system, and is largely influenced by disturbances, the phenomenon is not entirely clear. Thus, improvement in the performance of the welding power source is useful for controlling a wave form of a welding current, a welding voltage or the like within a certain micro-time and for stably maintaining an arc between electrodes. Currently the welding conditions are set by relying on the experience of the operator.
As a technique of automatically setting welding conditions, there is a method described in Japanese Patent Unexamined Publication No. 59-159272, in which a welding condition is easily obtained by using a simple relational expression.
Further, there is a method described in Japanese Patent Examined Publication No. 7-47209, which comprises the steps of storing a plurality of welding parameters, determining the other welding parameters one by one in accordance with a plurality of production rules and determining a welding condition for one welding path by repeating the above steps. There is also a method described in Japanese Patent Unexamined Publication No. 5-57436, which comprises the steps of storing into a data base a welding condition corresponding to a set condition, searching the data base for a welding condition coinciding with an inputted set condition, estimating a welding condition by using a welding condition data estimating portion constituted by a neutral network when the welding condition is not present in the data base and, if the welding result is good, registering all the welding conditions in that case into the data base.
There are rarely enough welding operators at a welding site, so there are many enterprises which promote automated and robotized welding. This is because a welding operator with a superior welding technique is usually of an advanced age, and a lot of labor and time are required for a new welding operator to master a welding technique. However, in the case of simply promoting the automation and robotization of welding, since the work required of the operator increases due to problems in handling the new apparatus and difficulties in setting the welding conditions, a lot of labor and time are required for the operator to master handling of the apparatus and techniques of determining welding conditions, and operation efficiency is lowered. In order to solve the above problem, it is necessary for an operation to be easily set, for a welding condition of a welding becoming an object to be easily set even by a beginner, and for collected welding information to be easily stored as absolute information.
However, in the conventional art, as described in Japanese Patent Unexamined Publication No. 59-159272, there is a method in which a welding condition is set by using a simple relational expression between a welding cross sectional area, a welding current and a welding speed. However a non-linear complex welding phenomenon of a multi-input and multi-output system can not be expressed only by the relational expression between a welding cross sectional area, a welding current and a welding speed (the welding cross sectional area can not be uniformly determined by the influence of scattered spatter and by the attitude of the work object), so that a highly reliable welding can not be obtained. Further, as described in Japanese Patent Examined Publication No. 7-47209, in order to set a welding condition, it is necessary to search many times for a parameter from the storing portion by using the production rule on the basis of the correlational condition between a multiplicity of stored welding parameters and a parameter till the welding conditions become all complete, thereby setting a welding condition. Since the correlation between the welding parameters and the parameter can be independently stored, it is possible to store each as a knowledge having high independence. However, a condition in a process for determining the welding condition is changed since the correlation between the welding parameters and/or the parameter is corrected and canceled, so that there is a problem in that the resulting welding condition becomes information having no reproducibility. Still further, as described in Japanese Patent Unexamined Publication No. 5-57436, since only the welding condition corresponding to the set condition is stored in the data base, there have been problems in that it is not known what results can be obtained if a welding is performed under the retrieved welding condition. If the corresponding welding condition is not registered in the data base, since the data estimating portion estimates the welding condition and, if the welded result is good, the welding condition capable of coping only by the welding condition data estimating portion irrespective of whether or not the welding condition is changed is recorded into the data base, and prolix data are contained in the database, so that there has been a problem in that useless date is generated and the retrieving speed is lowered.